Arrangement for the production of musical sounds by electrical means



April 1936- v F. TRVAUTWEIN 2,039,201

ARRANGEMENT FOR THE PRODUCTION OF MUSICAL SOUNDS BY ELECTRICAL MEANS Filed June 5, 1931 5Sheets-Shoot 1 April 28, 1936. F. TRAUTWEIN 2,039,201

ARRANGEMENT FOR THE PRODUCTION OF MUSICAL SOUNDS BY ELECTRICAL IEANS Filed June 5, 1931 5 Sheets-Sheet 2 April 28, 1936. 2,039,201

ARRANGEMENT FOR THE PRODUCTION OF MUSICAL sounns BY ELEC1 RICAL MEANS F. TRAUTWEIN 4 Filed June 5, 1951 5 sheets-she's; s

A ril 28, 1936. F. TRAUTWEIN I 2,039,201 ARRANGEMENT FOR THE PRODUCTION OF MUSICAL SOUNDS BY ELECTRICAL MEANS Filed June 5, 1931 5 Sheets-Sheet 4 Fig.13

April 1936- F. TRAUTWEIN 2,039,201

ARRANGEMENT FOR THE PRODUCTION OF MUSICAL SOUNDS BY ELECTRICAL MEANS Filed June 5, 1931 5 Sheets-Sheet 5.

J7 Twain 61172 Patented Apr. 28, 1936 UNITED STATES ARRANGEMENT FOE, THE PRODUCTION OF MUSICAL SOUNDS BY ELECTRICAL MEANS Friedrich Trautwein, Zehlendorf, near Berlin, Germany Application June 5, 1931, Serial No. 542,400 In Germany March 24, 1930 '7 Claims.

It is already known in the art that it is possible to produce musical sounds in such a manner, that electrical oscillations are produced with the aid of expedients known in conjunction with elec-' tro-technics, e. g. electronic valves and are rendered audible by means of loudspeakers. Furthermore, it is also-known, that to these tones certain timbres may be imparted by mixing fundamental oscillations and harmonic vibrations or overtones in certain proportions.

The present invention is now based on the following important and new discoveries:

A large number, particularly of the characteristic timbresof musical instruments, as well as the voice sounds, ar created by the so-called sound formers. These are oscillation impulses, mostly damped, of oneor of a plurality of fundamental frequencies being created in the course of a period of the fundamental tone and gradually fade in the'course of such period. The frequency of the sound-former is, therefore, higher, than that of the fundamental tone, being however,-in' contradistinction to Helmholtz theory, which recognizes harmonic overtones only,generally not harmonic with the fundamental tone, but may also be harmonic. The sound-formers are-mostly created by shock ex-' c lters of one or of a plurality of resonant bodies. The shock is released by the fundamental oscillation and that in most cases by the fact, that the curvature of the fundamental oscillation shows one or a plurality of discontinuities.

In accordance with the present invention two different frequencies, as a matter of principle, are

produced, being associated with each other in a certain manner. The first frequency. group is to impart the timbre to the tone produced, whilst the frequency of the fundamental tone isdetermined by the second frequency, which is mostly lower than the first .frequency group. In ac cordance with the present invention these two frequencies are not simply added, .but are interlinked with each other in a different manner. In conjunction with this interlinking it is, however, essential, that certain first frequencies or frequency mixtures decisive in regard to the character of the musical sound and constituting the sound-former, are rhythmically varied in their amplitude corresponding to the frequencyor frequencies of the desired fundamental tone or tones Csecond'frequencies).

In the accompanying drawings the present in'- vention has been shown by way-of example, in

which Figs, l to 1 show various oscillation diagrams,

Figs. 2 and 3 different diagrammatic views in accordance with the present invention,

Fig. 4 is a diagrammatic view for mutually infiuencingthe oscillation producers in accord-' ance with a further form of performance, 5

Fig. 5 represents a perspective view of a play ing device in accordance with the invention,

Fig. 6 shows a schematic representation of a special example of performance in accordance with Fig. 5, whilst Figs. '7, 8, 8 and 9, as well as 9 are fragmentary views of parts ofthe arrangement in accordance with Fig. 5',

Fig. 10 is a diagrammatic view of a further modification constructed in accordance with the invention,

Fig. 11 being a side View of a still further modification of the invention in accordance with Fig. 5,

Fig. 12 is a cross section through the arrangemerit in Fig. 11,

Fig. 13 is" a diagrammatic view of the present invention applied to polyphonic appliances,

Fig. 14 is a diagrammatic view of a recording device in accordance with the present invention, Fig. 15 illustrates a diagram of a special part of the diagram in accordance with Fig. 3,

Fig. 16 is .a diagrammatical view of the arrangement in accordance with Fig. 15, and

Fig. 17 is a further form of an electromagnetic musical instrument, I I p Fig. 18 shows a complete op'erative instrument, the parts of which have been shown in theother figures.

In Figs. 1 to 1 the chronog'raphiccourse of series of oscillations has been shown, (1', in Fig. 1 showing the schematic representation of a fundamental series of oscillations with two discontinuities, b, in Fig. 1 a'similar series of oscillations, but as differential quotient of a in Fig. 1. c in Fig. 1 represents a series of damped oscillations, as created by shock excitation of a resonant body by oscillations of the shape a or. 12, whilst d in Fig. 1 represents the oscillation composed of the oscillations a and-c. A comparison of the oscillations c or d with oscillographic records of musical sounds reveals an excellent conformity.

Figs. 1 to 1 show the-result of an examination of the oscillations of a violin. The curve a shows 50 the movem ent-of a point of the string played on with the bowI This vibration is first 'of all inaudible. It takes place intermittently, the stringbeing taken along-by the bow until a certain tension in the string is produced. Owing to this 55 tension, the string suddenly or intermittently returns until it is again engaged by the bow. The whole procedure begins again. The curve b represents those oscillations which in consequence of the momentum of inertia of the oscillating parts act on the resonance body of the instrument. It is obvious that new natural vibrations of the resonance body will result from each amplitude. The natural vibrations of the resonance body remain substantially the same. Merely the series of shocks or impulses is varied by shortening or lengthening the oscillatory section of the string. The natural frequency of the wooden body is fundamentally dependent on the frequency of oscillation of the string. Consequently, the beginning of a period of the fundamental oscillation is not the same as the beginning of a period of the resonance vibration. ".t is obvious therefrom that the vibrations of the resonance body which determine the tone or sound character are not harmonic with the fundamental frequency which determines the pitch of the tone. The present invention is based on this fact. While according to the hitherto valid Helmholtz" theory, the vibrations determining the tone or sound character represent harmonic oscillations of the funda-- mental tone, unharmonic vibrations determining the tone or sound character are produced by the fundamental tone according to the present invention. Consequently, in order to reproduce sounds, a distorted fundamental tone was hitherto the starting point, the harmonic oscillations of which were eliminated according to requirement, while according to the present invention two frequency groups are produced'which are coupled together in a special manner. The first frequency group determines the Hall formers. It is advisable to allude to a group because it may be a question of several individual frequencies. With regard to these frequencies, it is usually a question of damped oscillations. Figure 1 shows an oscillation diagram wherein a Hall former frequency is caused to vibrate rhythmically. In contradistinction to the Hall former frequency or frequencies, the frequency or frequencies with which the impulsing is effected is regarded as the second frequency or frequency group. While the first frequency group determines the sound character of the tone, the pitch of the tone results from the second frequency group. It is clearly obvious from the curves of Figs. 1' to 1* what is implied by shock or impulse excitation. Figure 1 represents periodically produced short Vibrations, from which the vibrations according to Fig. 1 result. This shock or impulse like ex-- citation may be compared with the playing on a string of an instrument. However, it must be taken into consideration that in the present case the rhythm of the touch determines the tone or sound while the oscillation of the string produces the tone color. The comparison with the playing on a string of an instrument is merely given for a better understanding.

For the electrical simulation of musical sounds, i. e. of oscillographs showing a course resembling the diagrams according to Figs. 1 and 1 there will, therefore, be the problem of producing or generating electric alternating currents, exhibiting the characteristic features of these oscillographs. Said alternating currents are then converted into sound with the aid of the loudspeaker, and, if necessary, by first amplifying. The characteristic of these'oscillations is the presence of first frequencies determining the tone color, the

amplitudes of which are varied in the rhythm of the fundamental tone. This rhythmical variation is suitably effected by means of electrical modulation methods, as they are known in conjunction with high frequency technics, in order to modulate a carrier in proportion to transmitter currents. Fig. 2 shows a diagram of connections being adapted to this purpose. In Fig. 2, IDI indicates a three-electrode tube the anode circuit of which is closed over a telephone I02, a transformer I03 and a source of anode current I04. I05 is the grid electrode which is connected over a voltage battery 106 and a transformer I01 with the cathode I08. Alternating current sources of relatively different frequencies are connected on the primary side of the transformers I03 and till. According to the present invention, one of these. two frequencies is regarded as the first fre quency and the other as the second frequency. Owing to the negative voltage of the grid Hi5, modulated oscillations are produced in the anode circuit which are formed from the two frequencies. The first frequencies are rendered active in the plate filament circuit, the second frequencies in the grid circuit. In connection herewith the curved part of the valve characteristic is acted on by a corresponding negative biasing grid voltage, so that a modulating eifect is created. The modulation of the carrier may naturally be effected in another manner which is also known in conjunction with high frequency technics, viz: by adding carrier and side bands in a suitable manner, creating as a result, hcwever, the diagram of a modulated oscillation.

Furthermore, in order to amplify the fundamental tone, the modulation frequency may be mixed again with the modulated oscillations in accordance with the oscillation diagram as shown in Fig. 1

The rhythmical variation may also be effected in such a manner, that the oscillation system for the sound formers are caused to oscillate by oscillations of an oscillation system for the fundamental tone for instance, the modulation which is known in the high frequency art.

A particularly advantageous form of performance of this principle consists in causing the sound former to oscillate by shock excitation.

For the electric production of musical sounds and voice resembling sounds, the combination of .'I

an oscillation producer with resonant formations is, therefore, necessary, the natural oscillations of which are lying higher than those of the oscillation producer, in connection with which suitable measures are provided for causing the if excitation of the natural motions of the resonant bodies to take place shock-like. Apart from selecting a form of oscillation with points of discontinuities, this may also be secured, f. i. by effecting the coupling of the resonant combination with the oscillation producer by means of an element, which shows discontinuity. Figs. 3 and 4 illustrate examples of performance representing electric connections. In Fig. 3 l denotes a gas-filled discharge vessel (gaseous conduction lamp with or without heated cathode, partly also with further electrodes, e. g. for joining auxiliary potentials) which, together with the condenser 2 and the resistance 3, produces electrical oscillations, the curvature of which is known to show discontinuities on igniting and darkening the gaseous conduction lamp. The electrical energy for the maintenance of the oscillations is obtained from the source of current 4. With the aid of the transformer 5 these oscillations are in the anode filament circuit of which a resonant.

combination, consisting of the self-induction I and capacity 8, is situated. Inorder to be able to adjust the damping and with it the period of the fading out, ad lib., the resistance 9, as ad ditional damping, and the back-coupling by means ofthe condenser II) as regeneration, have been provided. For the purpose of regulating the degree of coupling, of the amplitudes and partly also of the damping, steady current resistances or complex resistances II and I2 may be provided in the grid circuit and in the anode filament. circuit. The, combined oscillation acts, .if need be in conjunction with the interpolation of amplifying means 6a, on the loudspeaker I3 or e. g. a self interrupting device.

"it may also consist of a string, tuning fork or else on a further amplifier interpolated at this point. the amplifier may be identical with the source of current 4. Fig. 3 is only to represent the underlying principle; the design as such naturally ad-' mits of many variations. For instance, another device may be made to serve as oscillation gen- .erator, furnishing a curve with discontinuities.

Electromechanical oscillation generators also have proved particularly adaptable, because'they yield in most cases marked points of discontinuities, as

Moreover, experiments have shown, that the sound former effects will also show themselves, if the discontinuity of the oscillation curve is not particularly marked, especially then, when the resonant combination is weakly damped. For instance, it will be possible to utilize the oscillation s .of an ordinary valve transmitter, provided they are C0llducted over arectifier or another means of def:

ormation, and it will be, a, o. found'sufficient, if the oscillation is taken from the plate circuit of a valve generator. The auxiliary means 9, ID, II

- and I2 shown in Fig. 3 are not absolutely.essential, nor is it necessary to consider the application of an amplifier as being of fundamental importance. It should be particularly pointed out, that the resonant combinations 1, 8 are not implicitly required to be of anelectrical nature,

the like electro-magnetically influenced, or also of an electrically influenced piezo.c rystal. Also the resonant bodies usual in the technics of mu-.

sical instruments, such as wooden bodies, tubelike formations and the like are adapted for the formation 'of sound producers, provided theyare influenced in a suitable manner, i i-. electro-magnetically by the electrical oscillation. A special example of performance of this latter idea concerns an electrical violin, (viola-cello, 'bass and similar instruments), being excited, instead of means of a .violin bow, by means of an el'ectromagnet 50, Fig. 17,. e. g. at the bridge, or with the aid of a ferro-magnetic string 5|, performing compulsory oscillations. It is true that such arrangements have already been made use of for experimental purposes. The essential feature of the present invention consists, however, therein, that the form of curve of the exciting oscillation current exhibits the mentioned discontinuities for the excitation of the sound producers. The form of curve of the glow-valve generator shown in Fig. 17, consisting of a glow-lamp 52 with condenser 53, a battery 54 and a rheostat 55, resembles the oscillation of the string excited by means 'of the bow, to such an extent, that through this combination the electrical excitation of the violin does not only constitute a' fully equal substitute The source of the plate current I4 of Fig. 4 represents, a connection, in which the discontinuity serving for impulsing the sound producer generator I5 has been transferred in a connecting member I6 between any desired oscillation generator I1 and the sound producer generator I5. As such connecting member may be used for instance, a glow-lamp, a negatively biased amplifier valve, arectifier or another element of distortion may be used. For some musical sound effects the. additive admixture of the fundamental tone to the oscillations of the sound producer is-of importance (see Fig. 'ld). With the aidof the couplings I8 and I9 jointly acting on the outlet 20, a mixture of fundamental oscillation and sound producer may be adjusted on in any desired proportion. At 20, the outlet leads, for instance, to the amplifier.

Speaking, singing and animal sounds are imi- 'tated with surprising similarity, by so adjusting fundamental tone and sound producer, as they are composed incenjunction with the corresponding natural sounds. The latter fact is of very great importance, not only from a scientific point. of'view, but also from a technical point of view. The artificial speaking or singing sounds are, considered from a musical point of view, of very great value, for instance, by installing 'as register in an .organ a device in accordance with Fig. 3 with adjustment of the sound producers for the produc- -tion of a vowel-like sound and variable fundamental tone.

The further elaboration of the present invention concerns arrangements for carrying out the process, especially for the construction of electrical musical instruments. In regard to a musione or of separate oscillation generators may be arranged to be adjustable. In the connection in accordance with Fig. 3, for instance, the pitch of the tone is determined by the rheostat 3 and the condenser 2, which latter may also be connected in parallel with the rheostat, or at both points condensers may also be provided. In view of the fact that the rheostat variation may technically be carried through in a very simple manher, this kind of adjustment for the pitch of the tone is preferred. In accordance with the present invention the manual, therefore, consists of a variblerheostat which is so arranged, that, by pressing down a wire, band or the like upon a rodtubeor suchlike shaped rheostat-bodies at certain points, certain resistance values will be interpolated which are assigned to certain pitches of tone; Fig. 5 represents a simple play-box. The resistance wire 22 stretched between its two holding points 2241 and 2217 allows at any point of its length of being pressed against the conductor 23 designed as a bar. In Fig. 5 the insulated plate 23a is designed as carrier for the holding pins 22a and 22b and the conductor 23. electric leads for the beginning and end of the resistance wire 22. 23 is the lead for the conduc- 220 and 22d are length of bar, it will be obvious, that the distribution of the scale resembles that of string instruments, i. e. the touches will be closer together as the pitch of the tone grows higher. It has now been rendered possible in conjunction with electrical musical instruments, by selection of the determination values, to arrange the play-range so as to be absolutely identical with that 'of a string instrument, in the manipulation of which a musician has become skilled. It will especially be possible to arrange a plurality of resistances, for instance I resistances 22, being assigned to 4 oscillation generators, in juxta-position and thus to imitate a customary string or other musical instrument in its manner of playing. A more perfect manner of playing is rendered possible, if the resistance distribution in dependance on the length is so arranged, that every musical tone interval corresponds to equal intervals, identical with the progression of notes on the piano, without, however, the limitation to separate chromatic tones, but with constant succession of the pitches of tone. This resistance distribution is attained, for instance, by selecting a variable cross-section of the wire, of which the resistance is made to consist, or by a variable pitch of the winding, by winding up the resistance wire on a specially formed body, as it is being shown in Fig. 6 by way of example, by a corresponding shape oi the resistance body of a highly resistive material or by taking similar measures. In Fig 6 227 indi cates a resistance body consisting of wound wire, of special shape, whilst 23c represents a contact wire stretched above it so as to be insulated, by the pressing down of which the corresponding resistance values are interpolated. Fig. 7 shows an other example of performance of the resistance body in an automatic musical device in accord ance with Fig. 5, 2.2g indicates a carrier consisting of a non-conductive material, viz. a. gut-string, by way of example. 22h represents the resistance wire wound up on the carrier 22g, the windings also being insulated from each other. This wire may also consist of resistance wire coated with lacquer. After having been wound up the outer edges of the winding body are brightened. A resistance conductor designed in such a manner is employed in the same way, as the resistance-wire 22 illustrated in Fig. 5.

In a similar way it will also be possible to bring about a variation of the pitch of tone by varying a self-induction, which then requires to be de-- signed in an arrangement in accordance with Fig. 6 in a manner corresponding to that of the resistance body 22f, but on a magnetically conducting material. duction may further be effected as a whole or part- 1y also by connection in parallel of the resistance or by short-circuit. A transposing instrument is thus obtained in a very simple manner, for in- The variation of the se1f-lnon the desired values with the aid of a resistance. resembling Fig. 5, connected as potentiometer and operable by key manipulation. In this case the heating battery may be used as potentiometer battery and the range of tension may be varied by means of a regulating resistance connected in series. In this case the transition from the logarithmical to the linear distribution of the pitch of tone along the play-board is attained by manipulating on a part of the valve characteristic being curved in such a manner, that the valve resistance as function of the potentiometer position shows the inverse course. Such ranges will be found in the characteristics of most amplifier valves or else such valves may be correspondingly dimensioned. The playing range thus yielded is suitably noted on the musical device by means of a scale 2| (Fig. 5) being wholly or partly displaceable. With the poten tiometer connection another playing range is created when pressing two points, (short circuit ing of a section) which is suitably noted as secondary scale. In another example keys instead of the scale 2! for the more rapid location of the pitch of the tone are employed; they are arranged above the musical device (Figs. 8 and 8a) The keys Zia are so designed as to be elastie and provided with a "ounded oii cushion Zlb of rubber, felt or the like, so that when using the keys it will be possible to produce tremolo eifects as with the finger. The keys have been freely arranged above the playing plane at a back wall Zic with such interval, that it is possible to pass the fingers between the keys and the playing plane and to so play, as it there were no keys. It is not necessary to provide keys for all tones; it will be suiiicient to provide keys at certain intervals, e. g. quints and quarts in order to guide the player. Another solution of the problem to guide the player without the necessity of looking away from the notes, has been shown in Fig. 9. This drawing shows a rollermetallic cylinder 60, with a clear space between them, arranged on the inside of the body 55 of insulating material. By deforming the body 55. contact will then be established between the me tallic cylinder 60 and the resistance winding 55. both the latter being connected with the osci1- lation generator in a manner previously dcscribed.

It is required in all cases, that the resistance determining the pitch of tone should be so arranged that when in a state of rest no produc tion of tone takes place. In connection with wire resistances this is a comparatively simple matter, it, with the contact wire not pressed, the electric circuit is interrupted. The use of an amplifier valve entails in the first instance the difliculty, that with an open grid, the valve resistance does not become infinitely great. This difficulty, however, may be met with, by provid ing at the grid a comparatively high negative biasing potential, so that when pressing down 58 is a 'main carrier low-frequent electrical oscillations, whilst 30 and 3| represent condensers provided for the purpose of varying the frequency of the oscillation generator. The frequency is further determined by a multi-electrode valve 32 being situated within its electric circuit. The resistance of this valve is. changed by providing different tensions at the control electrode 33 opposite the cathode 34. The variable tension may be taken from a heating battery-35 and that in conjunction with the interpolation of a musical device as shown, for example, in Fig. 5. The bar 23 is connected with the source of tension 28 via a-potentiometer 42, so that by pressing'down the wire 22 the electric circuit to the source of current 28 will be closed. The bar 23 is, moreover, connected with the control electrode 33. Moreover, in this electric circuit the high, negative biasing potential 41 .has been interpolated, acting entirely on the grid 33, if there is no contact between 22 and 23. If this contact is established, the biasing potential 4| will act only partly to that amount .which may be gathered from the position of the potentiometer 42. To this amount of tension must be added, moreover, the partial tension of the battery 35 which is derived from the position in which the resistance 22 with the bar 23 is placed to the contact. This causes the resistance of the valve 32 to be varied, whereby the fre- 'quency of the oscillation generator 29 will be determined. It has already previously been mentioned herein, that the valve 32 requires to be usedon such a section of the characteristic,

which is assisted by a correspondingly biased auxiliary grid 33a, that through the-medium ofequally large sections on the wire 22 uniform variations of tone are attained. The frequency thus produced is passed on to a suitable reproduction appliance via a transformer 36. For the purpose of simplifying the'diagram of connections, the arrangement according to Fig. 10 shows, for the purpose of varying the intensity of the sound, merely a variable leak resistance 31, and 38, and for the purpose of varying the timbre of the musical sound, merely condensers 39 and 40.

- nected therewith. In accordance with the present invention this difiiculty will be removed by leaving the rare-gas tube in astate .of medium current passage and only then bringing about the release of thetone by pressing down the contact wire. This may, for instance, be effected in such a manner, that the one pole of the condenser 3I shown in Fig. 10 is connected with the bar 23 instead of with the cathode, in connection with which the resistance of the tube 32 m a position of rest possesses a finite value, e. g.

In connection herewith, the sec-' ondary winding of the transformer 36 and theby reduced tension of the-battery 4|. In this case the-rare-gas tube, being in a state of rest, does not perform any oscillations, as far as the condenser 30 is missing. The arrangement may, however, also be of such nature that, when in a state of rest, the grid is left open, in connection with which the rare-gas tube may oscillate also when in a state of rest and the action on the loudspeaker may be obviated by placing an interruption somewhere in the train of the further connection, for instance in an amplifier step, which is bridged by pressing down the contact wire 22, or else it may be rendered possible to neutralize by this pressing down a high negative grid tension.

For the purpose of applying this method to a quired, to create dynamicdiiferences, which may be produced by the player easily and in an artistically effective manner.

A special manipulation of the loudspeaker regulator by hand is not advisable, because this would require too much attention on the part of the player and, moreover, prevents him from using both hands for playing. A manipulation by means of a foot pedal is obviously preferred, in connection with which a steady or stepwise manual regulating means for the coarse adjustment may be admitted, whilst the artistic shading of the intensity of sound is effected by means of a pedal, similar to that used in playing on an organ. As switching element, the loudspeaker regulator consists of the resistance 38 in Fig. 10. The most perfect method of loudspeaker regulation is effected by the same movement, as the tone release, for instance, by causing the whole valuable musical instrument it is further reof the playing board to be elastically or'displaceably supported and to be so connected with a regulating element that on effecting the pressing down for the purpose of releasing the sound, the intensity of the sound is influenced according to the intensity of the pressure exercised; The

construction shown in Figs. 11 and 12 is highly adapted for this purpose. The under-side of. the metal bar 23 carries the arrangement 25, .consisting of two electrodes with carbon powder 26 placed in-between the two electrodes. By pressing down the upper electrode the carbon powder is compressed, thus varying its electric resistance. The connection must then be so selected, for instance, with the aid of an amplifier valve, that with a low resistance the intensity of sound is enhanced. The dependance of the carbon resistance on the pressure adapts itself better to the physiological sensation of the intensity of sound than a linear regulation. If the carbon powder is omitted from the construction described above and replaced by adielectric, a condenser will be produced, which is variable by pressure,

and which may also be made use of for the purpose of sound regulation. The comparatively small capacity values are sufiicient, if, in an amplifier connection the condenser, is connected e. g. with a high grid leakage .resistance in parallel.

The most important perfection which is embodied in the present invention forv the technics of musical instruments, is the adjustment of the timbre of the musical sound by means of the sound producer at will.- In view of the fact, that the sound producers remain constant 'over al considerable range of pitch, they may be switched in register-like in the same way as with an organ. For widely separated ranges of pitch, other sound producers or sound producer combinations will have to be considered. For this reason it is preferable to assign to different ranges of pitch different sound producer combinations.

For the purpose of attaining further musical effects, the timbre, in accordance with the present invention, too, is rendered constantly variable. It will be gathered from Fig. 3, that the timbre, for instance, may be influenced by the regulation of the condenser 8. The adjustment of the condenser B may, e. g. be combined with the sound release in such a manner, that by displacing the playing board in a horizontal direction, a suitable mechanical coupling of the condenser 8 is regulated. A foot-pedal, too, may be used for that purpose.

The uniform or stepwise influencing of the timbre is not limited to the sound producers. The possibilities of influencing, well known in the art (preferably condensers, inductivities, resistances and their combinations), given timbres by preferring or adversely affecting single frequencies or frequency ranges, or by the overtone synthesis, may be combined with the musical instrument in accordance with the present invention.

In consequence of the uniform variability of the intensity of sound and timbre, an artistic manner of playing is created, being attained with the aid of a three-dimensionally movable or manipulatable arrangement, in connection with which pitch, intensity of sound and timbre have been assigned to the dimensions. In the musical device in accordance with Figs. 11 and 12, 23 represents a metallic bar of, say cm. length, above which a resistance wire 22 has been so stretched as to be insulated. 2 l-represents a spring for the purpose of ensuring a yielding support for the bar 23, so that the bar may be displaced in a downward, as well as in a lateral direction. By moving the bar in a downward direction, a regulable resistance of carbon powder 26 depending on pressure and arranged, by way'oi example, between two plates 25 is controlled, the resistance influencing the intensity of the sound. The movement of the bar in a lateral direction according to Fig. 12 produces, for instance, by the regulation of selective circuits with the aid of a condenser 2! Variations of the timbre. The pitch of tone, however, is determined by pressing down the wire 22. In connection herewith the arrangement is preferably of such nature, that in one of the surfaces a plurality of musical devices of diiferent timbre have been arranged in juxta-position which through the means already described, possess the same pitch of tone at any point of the other direction of the surface. In connection herewith it may be of importance that the sequence of timbre of the separate musical devices corresponds to a transition from the soft to the hard timbre which is continuous as far as possible.

The musical instrument described in the foregoing yields, apart from those already mentioned, a number of other musical effects. If the frequency of the fundamental tone drops below the limit at audibility, the sound producers convey the impression of sounded bells, xylophone-rods or triangles. By sounding the sound producers, for instance, by switching in the working current at certain intervals, rhythmical eilects will be caused. The rhythm is in this case produced by oscillations below the limit of audibility of the rare-gas tube l as shown in Fig. 3 and differs according to the point of the playing board on which the contact wire is pressed down. In this way it will be possible to produce drum or xyiophone rolls at a, tempo impossible of production by hand. Atonal noises, such as drum are caused by rhythmical glow discharges or by switching in the working current acting on the loudspeaker 5 and not by switching in the sound producers. Apart from impulsing the sound producer for the purpose of generating fading out oscillations, that is those of a piano-like character but with any desired timbre, they may be produced by artil0 fically imparting to the oscillations a fading out character, for instance, by taking the anode potential of an amplifier step from a charged condenser which during the intervals is always charged up again by suitable means. 15

In order to produce electric music, those ampli fying and loud speaking devices may be used which are already provided in radio receiving apparatus. In this case merely commutators are to be provided for changing the device for radio 20 reception or for producing electric music. In special cases, the receiver as well as the means for producing electric music may be allowed to operate simultaneously on the same loud speaker.

The forms of construction of the present inven- 5 tion of an electrical musical instrument is not confined to one-tone instruments or to instruments with a small compass of tones. On the contrary, pianoor organ-like instruments may be constructed in accordance therewith, in con- 30 nection with which a continuous scale of tones may, nevertheless, be .retained, so that, when pressing down several points of the playing board, all tones sound simultaneously appertaining to the points pressed down. This may also be attained by causing several tone producers to work at a common playing board in accordance with Fig. 3, by arranging the wires, bands or the like parallel to each other in juxta-position or in tandem, so that to each tone producer only a 40 small interval, about a small or minor third is assigned, the next one on the playing board immediately joining thereon. It will then be pos sible to play several tones simultaneously only at intervals of more than a minor third, which, in 45 most cases, will be found suiilcient. A musical device, consisting of a plurality of wires 22 or the like, switched on to the same tone color or to diiferent tone colors, may be so elaborated, that the wires are covered by a yielding strip of insulating material, on which the playing range has been suitably drawn. By way of explanation, it may be added that with the majority of musical instruments all simultaneously played notes sound with substantially the same tone color. For instance, 5 another tone color would not be possible'with the violin. However, it would be possible with the organ which has several keyboards. In contradistinction to the organ, according to the invention, tones played simultaneously on one and the same playing mechanism have selective different tone colors. A more perfect arrangement for playing with many tones is secured, by assigning to each finger a special oscillation generator, each being identical with the other. In this case the instrument will be mainpulated with gloves on the 1 hands, each finger of the gloves being provided with a metallic contact. Leakance takes place by light flexible wires which do not hinder playing. The regulation of the sound amplifier may be effected in this case by placing in finger tips of each glove a small quantity of carbon powder with soft electrodes such as tin-foil.

Further elaborations of the invention involved 75 devices for polyphonic play with a key-board, especially resembling that'of the organ. In regard to this field of application the production of the musical sound by' sound producers is of preeminentimportance, because in connection herewith a separation of fundamental tone and timbre is present, i. c, it will be possible to assign to one and the same fundamental tone any desired timf bre and also simultaneously a plurality of timbres.

any desired number and frequency adjustment.v

In order to be able to rapidly adjust certain, frequently recurring timbres, it maybe advisable to provide a number of fixed combinations of sound producers, which may be switched-in stop-like. As a matter of principle, however, sound producers, if they are uniformly variable in their defin ing magnitude (natural frequency, damping and ratio of amplitudes) allow of adjusting all possibletimbres. For a perfect musical instrument not only fixed combinations are provided, which may be manipulated with all known means of technics' (stops, roller-swell and the like), but also sound producers, allowing any desired adjustment, for. the purpose of attaining special timbres. These adjustable sound producers are ,suitably wholly or partly so designed, that they are not switched in during their adjustment. The activity of the player extends then also to the combination of the timbres by preparing adjustments of sound producers, which, duringthe play, may be treated like fixed stops, but may also be modified at will, if desired.

The number of fundamental tone producers may also be considerably limited, in view of the fact, that it is possible to control with one fundamental tone producer the monotonic tone range. It will, for this reason, be sufficient to provide as many fundamental tone producers as should maximally be sounded at the same time, for instance, l for a key-board and 2 for the pedal. For the purpose of dealing with this problem an example of performance for an arrangement is dealt with in the following, in which by means of an automatic selective switch system, resembling the automatic telephone exchanges every key pressed down, selects a free system. The systems are accurately and equally attuned amongst themselves, so that it is without any influence on the pitch of the tone, as to which system the selector switches on a pressed down key. A wiring diagram of a suitable four-part selective arrangement is shown in Fig. 13. To each key 62, for instance, four relays 6| with two break-contacts each have been assigned. The first and the last three keys may be provided with less relays. The horizontal 63 is the contact collecting bar of the keys. By way of example, the first, third and fifth key are supposed to have been pressed down. It will be seen, that the first key auto matically selects the first fundamental tone systom 64, the third key the second fundamental tone system 65 and the fifth key selects the third fundamental tone system 66. If now, for instance, the second key were to be pressed down, this would select the second fundamental tone system 65, whilst immediately the following keys pressed down would jump to the next following fundamental tone system 68 or 61. It should be pointed out, that this selective system with its, special modus operandi is merely an example of performance andv that other selective systems may also be made use of In a simple formqjof performance of an organ-like instrument, the relays 6i may simultaneously be designed as operating magnets which, by pressing down a string at the corresponding point of the bar 23 release the tone. The arrangement, may, however, also be of such nature, that apart from the two break contacts at each relay 6| an operating contact is provided, being adapted to switch in the necessary amount of resistance required for the tone.

It is, moreover, possible to impart to each of the four musical sound generating systems a spethe organ, which during the play, provides a change of timbre of each separate part.

In accordance with the present invention it will be possible to attain by electrical means a tremolo change of the pitch of tone, of the intensity of sound and of the timbre. In order to attain such a tremolo change, the electric circ-uit which has to be considered in connection herewith is superposed by a slow alternating current, viz. for the tremolo of the intensity of sound of the electric circuit of an amplifier step (see H1 in Fig. 10), for the tremolo of the pitch of tone the gaseous conduction lamp circuit (see H in Fig. 10) and for the tremolo of the timbre the sound producer circuit (see I2 in Fig. 10). In

the latter case the alternating current 12 should instance, be effected electro-magnetically. A

conversion of the oscillations into sound would only then be required, if it were desired to overhear during the reception.'

,The introduction of magnesia into the glow conduction lamp vacuum renders the glow conduction lamp with magnesia charge particularly adapted for the electrical production of musical sounds in self-excitation connection.

The presence of magnesia in the gaseous conduction lamp is also favourable for securing a rapid starting and interruption of the ignitions. This propertyof the gaseous conduction lamp is important for the expelling of the sound producers, not only when producing the fundamental tone by self excitation of the gaseous conduction lamp, but also then, if the gaseous conduction lamp only serves to so chop a fundamental oscillation produced somewhere else, that it is rendered suitable for impulsing sound producers. A

further means for the purpose of attaining a strong shock effect will be found in the multiple application of gaseous conduction lamps, if necessary in connection with regulating means for the tension and auxiliary tensions.

An important expedient, particularly for the purpose of. securing a constant tune is embodied in the principle of the frequency transformation. In the upward frequency transformation a frequency multiplication in integral multiples takes place, in the downward frequency transformation a division by integral divisors. The tones thus produced are, therefore in a harmonic relation. The frequency division is particularly suitable.

It is produced by interpolating in the circuit pi-' loting the fundamental frequency a gaseous conduction lamp with parallel condenser (see 13 in Fig. 4). By suitably dimensioning this condens-- er it may be attained, that a tension peak show,- ing itself, charges the condenser to an amount which does not suffice for igniting the gaseous conduction lamp. 0n the other hand, the second, and if necessary, several following peaks, may lead to a tension summation sufficient for the purpose of igniting the gaseous conduction lamp.

The ratios may be so selected, that only each 2nd, 3rd, 4th, and so on tension peak will result in an ignition, so that the frequency, forthat rea son, sinks to the 2nd, 3rd, 4th part and so on. In this way an alternating current of an interrupting nature is created, being particularly suitable for impulsing sound producers. In connection herewith the original alternating current may be emanate from oscillation systems with considerable frequency constancy, as for instance, tuning forks in electric self-excitation, sirenes with ac-v curate regulation of revolutions or the l ke.

For a polyphonic musical instrument it may further be of advantage to so combine a selective system with frequency transformers as suggested in Fig. 13, that the fundamental-octave is formed in accordance with the selective system, 'whilst the deeper or higher octaves are formed by frequency transformation.

For some purpose the problem of imitating a room acoustics has to be solved. One means for producing such a reverberation, the application of which, as a matter of fact, is not limited to tones produced by electrical means, consists in gramophonically recording the reverberation, followed by a reproduction once or several times, in connection with which the interval of time between the reception and reproduction or between the separate reproductions corresponds to the desired reverberation duration and is suitably rendered adjustable. In Fig. 14 an example of performance has. been schematically illustrated. The steel disk 14 rotates in the direction of the arrow 15. Instead of a steel disk a. steelwire or band, both ends of which have been joined, may also be used. 16 represents a recording magnet provided at the oscillation generator, 11 and 18 are, by the way of example, two reproduction magnets, each of which being connected with an amplifying device, the outlets of which are connected with the original circuit in the desired amplitude ration. At 19 a quenching magnet has been provided. The duration of the reverberation may be adjusted by the rotary speed of the disk 14 or by a different arrangegreater than the peak value of the sound producer. The acoustic property of such an oscillation is partly favourable, partly undesirable for the musical employment. The great carrying capacity of the tone, that is the property of the tones to be audible from amongst a'tone mixture, is a favourable feature of such oscillation. This property seems to be parallel with the audibility over great distances. In this case it does not only depend upon the efficiency of the sound wave, that is on the mean value of the sound ef fect, but also on the peak values. An oscillation with great peak values may, in spite of an inconsiderable total efficiency, possess a considerable carryingcapacity. On the other hand, an oscillation with great peak values in conjunction with a low total efficiency, will not always be agreeable musically, the character of the musical sound. being sharp and shrill. Owing to this recognition the height of the peak values will be influenced by electrical expedients in accordance with the present invention. Fig. 15 shows a connection suitable for this purpose, as an example of performance. In this instance the two valves 80 and iii are to take the place of the valve 6a shown in Fig. 3. The characteristic of such a two-valve arrangement has been shown in Fig. 16. As ordinate, values i. e. have been plotted the current intensities appearing between the points 82 and 83 in dependence on the tensions e. g. established between 84 and 85. The two-,valve arrangement has, therefore a. limited transmitting range, which may be adjusted at 'willby dimensioning the biasing grid voltage 86 and 81 in the two valves. By means of this dimensioning'it will, therefore, be possible to shorten the peak values of the impulsing oscillations to any desired extent, whilst the passage for the producer osciloscillation-frequency of the said second generator, and the second generator provided with a regulator adapted to vary the frequency of the said second generator.

2. In an electrical musical instrument according to claim 1 the said first generator consisting of an electric oscillatory circuit and the said second generator containing in a circuit a glow lamp, a resistance, a condenser and current source, the said resistance being designed as regulable resistance.

3. In an electrical musical instrument according to claim 1, means in the said first generator adapted to vary the frequency of the damped oscillations.

4. In an electrical musical instrument according to claim 1, the said regulator consisting of an electric resistancewire stretched freely between two fixed points, a contact plate below the resistance wire yieldingly arranged parallel to a sliding of the finger of the player on the resistance wire. a

-6. man electrical musical instrument, a first generator producing damped electrical oscillations of a frequency in audible range, a second generator or producing undamped electrical oscillations of a frequency in audible rangeand an electric coupling between the first and thesecond generators adapted to start thesoscillations or the first generator in regular sequence, the frequency of the said sequence corresponding to the trlcal oscillations of a frequency in audible range, a plurality of second generators producing undamped electrical oscillations of a frequency in audible range, an electrical coupling between each pair of said first and second generators adapted to start the oscillations of the first generator in regular sequence, the frequency of the said sequence corresponding to the oscillation frequency of the said second generator, a plurality or regulators each adapted to vary the frequency of a said second generator, a keyboard, a selective system after the manner of automatic telephony between the said regulators of the generators of the said second type and the keyboard, the selective system being adapted to connect each depressed key of the keyboard only with one of the said regulators. FRIEDRICH TRAUTWEIN. 

